The Excel NORMSINV Function

The Standard Normal Distribution is a simplified version of the
Normal Distribution Function which arises when the mean of the distribution is 0 and the
standard deviation is 1.

Therefore, the Excel Norm.S.Inv function is the same as the
Norm.Inv function with
the mean and standard_dev arguments set to 0 and 1 respectively.

The Standard Normal Cumulative Distribution function and the Inverse of this function are shown in the graphs below:

Standard normal cumulative distribution function

Inverse cumulative distribution function

NORMSINV & NORM.S.INV Functions

In Excel 2010, the NORMSINV function has been replaced by the
NORM.S.INV function, which
has improved accuracy. However, the Normsinv function is still available in Excel 2010 (stored in the list
of compatibility functions), to allow compatibility with earlier versions of Excel.

Basic Description

The Excel NORMSINV function calculates the inverse of the Standard Normal Cumulative Distribution Function for
a supplied probability value.

The format of the function is :

NORMSINV( probability )

Where probability is the probability value (between 0 and 1), for which you want to calculate the inverse
of the standard normal cumulative distribution function.

Note that Excel uses an iterative method to calculate the Normsinv function and seeks to find a result, z,
such that NORMSDIST( z ) = probability.

Normsinv Function Examples

The spreadsheet below shows examples of the Excel Normsinv Function, used to calculate the inverse of
the Standard Normal Cumulative Distribution Function for 3 different probability values.

The formulas are shown in the spreadsheet on the left and the results are shown in the spreadsheet
on the right.